Rubber composition and method of preserving rubber



Patented Sept. 6, 1938 PAT OFFICE RUBBER. cQMIoSiTIoN AND METHOD 0F 7 r nisnrtvnvd RUBBER N0 Drawing.

Original application January 22,

" "1931,Serial.Nof510,514.' Divided and this applicationlfiarchfiq 1935, Serial No. 12,041

. This invention relates to the art'of 'rubber manu a u "and partic lar to th preparation, of rubber' compositions which" resist deterioration "due to aging or; to exposure to the atmosphere. 6 It has long been known that such deterioration canbe greatly retardedby" treating thejrubber either before or after vulcanization with certain substances known fasfage-resisters or anti-oxidants. The chief object of 'this'inve'ntion, then, is to provide a new and superior'cla'ss of antioxidants for rubber.

The substances which are employed as antioxidants according to this inventionare all ter- 'tiary aromatic amines containing two amino groups. The preferred compounds are those in. "which the two amino groups contain both aliphatic and aromatic substituents; The nucleus of the compounds 'or the'external substituents may, however, contain other substantially neutral group ngs, such as those of ethers and thioethers. Compounds in which the nitrogen'or the oxygen or sulphur form part of a heterocyclic ringhave properties differing considerably "from those of n the compounds of this invention and are notordinarily designated either as amines or as ethers; hence they are not included'within the scope of this invention.

I For example, the following symmetrically sub- 'stituted tertiary amino compounds are typical 30 members of the class of substancesfoutlined above: di-p-phenetyl dimethyl ethylene diamine,

diphenyldimethyl .diamino ldiethyli ether, tetraphenyl ,di amino diethyl ether, diphenyl ,dinapht 1 'di'aininodiethyi" ether, diphe'nyl dimethyl diaminofdiethyl sulphide, tetrar'nethyl di'a'mino 'diphenyl'ether', and tetramethyl'fdiaminc diphe nyl "sulphide. It will be understood," however that similar unsymmetrical compounds containing two or more tertiary amino groups may likewise be employed with good efiect.

The methods employed in the preparation of these substances will be evident to any skilledgorgarlic chemist, hence it will not be necessaryflto refer in detail, to the procedure. However, the 4 preparation 'ofthes'e substances may well'be illustrated by the fact that many of the substances may be prepared by reacting a secondary aromatic amine with a halogenated organic compound such as a dihalogenated ether.

50. Any one or a mixture of several of the aboveenumerated substances or of other equivalent substances falling within the same class may be incorporated into rubber with good effect on its age-resisting properties. For example, from 55 to 5% of such an anti-oxidant may be mixed with .jgation of 723%. "Geer oven it still had a strength of 2928 pounds "and anelongation of 57 7 and after aging in the the rubberbefore vulcaniaatiomthe antieoxidant having substantially no accelerating effect and therefore ordinarily not necessitating an ad'- justrnent of vulcanizing conditions. Alternately the antioxidantmay be applied to the'surface 5 of crude or vulcanized rubber, say inthe form of a powder, paste, or solution. Rubber so treated resists the deteriorating influence of age andjexposure to the elements far better than similar untreated rubber. 10 As a specific example of one embodiment of the method of this invention, a typical tire tread composition was prepared containing: blended plantation'rubbers approximately 100 parts'by weight, sulphur 5.5 parts, zinc oxide 30 parts, gas black 40 parts, mineral rubber 10 parts, palm oil 5 parts, and hexamethylene tetramine 0.75 part. This was divided into portions to one of which was added 0.95 part (0.5% of the weightof the composition) of tetraphenyl diamino diethyl 2 0 ether. The compositions Werethoroughly mixed, and vulcanized in a press for 45 minutes at 145 C. (294 F.) to produce an optimum cure. The relative rates of aging of the vulcanized compositions were compared by measuring their respective tensile. strengths and elongations bef ore and after aging. Accelerate-d aging tests were carried out in theGeer aging oven, in which samples were maintained at a temperature of 70 C. (158 LFQ) ina constantly renewed stream of air, as well as in the Bier'er-Davis bomb, in which other samples were maintained at thesame temperature (70 C.) in an atmosphere of oxygen at a pressure-of 300 lbs. per sq.'in. The composition containing the anti-oxidant had a tensile strength of 3936 pounds per square inch and ultimate elon- After accelerated aging in the pounds and an elongation 'of 623%; The same rubber composition when vulcanized and tested under the same"conditionslwithout thefanti oxidant deteriorated f r om an original tensile strength of about 3600 'pounds"pen'square inch :Bierer-Davis bomb it still-had a strength or 2767 and ultimate elongation of 640% to only 1830 pounds and 435% after 7 days in the Geer oven, and 760 pounds and 335% after 48 hours in the Bierer-Davis bomb.

It is evident from the above example that rub- 50 ber compositions containing even small proportions of the anti-oxidants of this invention resist deterioration far more effectively than similar untreated compositions. Other anti-oxidants of this class give similar results.

- derstood. Other similarly constituted substances containing a single tertiary amino group such as dimethyl aniline or dimethyl phenetidine have no appreciable effect on the aging of rubber. It appears, therefore, that the presence of at least two tertiary aromatic amino groups in the molecules of the compounds is essential to the present invention. I

Obviously, the practice of this invention is not limited to the specific rubber composition given above, such composition being merely illustrative. of one manner of employing the anti-oxidants of this invention. The anti-oxidants maybe employed in conjunction with other known anti-oxidants, or with other vulcanizing agents or accelerators than those here specifically disclosed. The proportions of the constituents may be varied, or other substances may be substituted generally therefonsince this invention is applicable to pure rubber 'or rubber compositions'of the most varied nature.

It is'to be understood that the term treating as employed in theappended claims is used in a eneric sense to include either the in rp a of the anti-oxidants into the rubber by milling or similar process,o'r their addition to the rubber latex before its coagulation, or to the application thereof to the surface of a mass of crude or vulcanized rubber. The term rubber is likewise employed in the claims in a generic sense to include caoutchouc, whether natural or synthetic, reclaimed rubber, balata, gutta-percha, rubber isomers and like products, whether or not admixed with fillers, pigme t vulcanizing or accelerating agents. This application is a division of my co-pending application, SerialNo. 510,514, filed January 22, 1931, which has matured into Patent 2,072,596, dated March 2, 1937.

While I have herein disclosed certain preferred manners of performing my invention, I do not thereby desire or intend to limit myself solely thereto, for, as hitherto stated, the precise proportions of the materials utilized may be varied and other materials having equivalent chemical properties may be employed if desired without departing from the spirit and scope of'the invention as defined in the appended claims. 1

I claimt.

1. The method for preserving rubber which comprises treating rubber with a tertiary aromatic diamine in which the amino groups are attached to difierent hydrocarbon groups of a compound selected from the class consisting of di-hydrocarbon substituted ethers and thi'oether's.

2. The method of preserving rubber which comprises treating rubber with a tertiary aromatic diamine in which the amino groups are attached to different hydrocarbon groups of a di-hydrocarbon substituted "ether.

3. The method of preserving rubber which comprises treating resents oxygen or sulphur.

comprises treating rubber with a tertiary diamino diaryl ether.

4. The method of preserving rubber which comprises treating rubber with a tetra-alkyl diamino diaryl ether.

5. The method of preserving rubber which comprises treating rubber with a tetra-alkyl diamino diphenyl ether.

6. The method of preserving rubber which comprises treating rubber with tetramethyl diamino diphenyl ether.

7. The method of I preserving rubber which comprises treating rubber with an aromatic tertiary diamino dialkyl ether.

8. The method of preserving rubber which rubber with a tetra-aryl diamino'dialkyl ether.

'9. The method of preserving rubber which comprises treating rubber with tetraphenyl diamino diethyl ether. v

10. The method of preserving rubber which comprises treating rubber with a tertiary aromatic diamine in which the amino groups are attached to carbon atoms of a thioether.

11. The method of preserving rubber which comprises treating rubber with an aromatic tertiary diamino'dialky'l sulphide.

1 2. The method of preserving rubber which comprises treating rubber with diphenyl dimethyl diamino diethyl sulphide.

13. A rubber compositionwhich has been vulcanized in the presence of a tertiary aromatic diamine in which the amino groups are attached to different hydrocarbon groups of a compound selected from the class consisting of di-hydrocarbon substituted ethers and thioethers.

14. A rubber composition which has been vulcaniz'ed in the presence of !a tertiary aromatic diamine in which the amino groups are attached to difierent hydrocarbon'groups of a'di-hydrocarbon substituted ether.

comprises treating rubber with a compound having the formula wherein A and A represent tertiary aromatic :amino groups and X represents oxygen or sulphur.

18. The method of preserving rubber which comprises treating rubber With a compound having the formula N-CHz-CHz'XOHz-CH2N R R wherein R'represent's an aryl group and X rep- WEBSTER N. ONES. 

